JP2007180937A - Method, device and program for accepting connection establishment request, and connection establishment request apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for accepting a connection establishment request, and a method and apparatus for requesting to establish a connection, capable of impartially processing a multiplicity of connection establishment requests. <P>SOLUTION: An establishment request detection section 31 detects a connection establishment request transmitted from each viewer terminal 2. Here, a SYN packet having a SYN flag set therein is detected as a connection establishment request. A hold time decision section 32 decides the hold time of the detected connection establishment request. An acceptance selection section 33 accepts the detected connection establishment request more preferentially as the hold time becomes longer, and returns a connection establishment response (SYN_Ack packet) to the accepted connection establishment request. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a connection establishment request accepting method, apparatus and program, and a connection establishment requesting apparatus, and more particularly to a connection establishment request accepting method, apparatus and program, and a connection establishment requesting apparatus that can accept a SYN packet in a TCP connection fairly.

  Researches have been conducted on technologies for detecting congestion of networks and routers to eliminate or alleviate them, or detecting signs of congestion and preventing them.

  In Patent Document 1, in order to control router congestion in an IP packet communication network, the queue size held in the TCP packet queue of the router is monitored. If the queue size is small, normal operation is performed. A technology is disclosed in which only a packet of an already established TCP connection is inserted into the queue when the size is increased, and a new TCP connection is suppressed.

  Patent Document 2 discloses a technique for prioritizing retransmission packets over packets other than retransmissions when accepting TCP packets.

Non-Patent Document 1 discloses a technique for uniformly discarding connection establishment requests (SYN packets) when congestion occurs in a network.
Japanese Patent Laid-Open No. 2002-314592 Japanese Patent Application No. 2002-552276 R. Mortier, et al., Implicit Admission Control, IEEE Journal on selected areas in communications, vol. 18, no. 12, December 2000

  In the TCP connection establishment request, if the response from the server to the SYN packet does not arrive even after the initial value of the retransmission timeout value (RTO) has elapsed, TCP determines that the SYN packet has been lost and retransmits it. Set RTO to double. If the response to the retransmitted SYN packet does not arrive even after the RTO has passed, the RTO is set to double and the SYN packet is retransmitted.

  That is, if the initial value of RTO is 3 seconds, the second SYN packet transmission is 3 seconds after the first SYN packet transmission, the third time is 6 seconds after the second SYN packet transmission, and the fourth time is the third time. 12 seconds after the SYN packet transmission, the fifth time is 24 seconds after the fourth SYN packet transmission. Such SYN packet retransmission is repeated until a specified time (connection timeout) elapses. For example, in the case of a Berkeley system, the specified time is set to 75 seconds by default. If the connection cannot be established during the connection timeout period, the specified time is processed as a connection failure.

  In this way, since the SYN packet of the TCP connection has a longer retransmission cycle for each retransmission, the hold time from the first transmission time for the retransmission packet is increased stepwise according to the number of retransmissions. Therefore, it is desirable that the accepting side accepts a connection establishment request with a long holding time with priority.

  In Patent Document 1, when congestion occurs, an establishment request for a new TCP connection is uniformly suppressed regardless of the length of the holding time. Patent Document 2 is a technique related to reception of a packet transmitted / received through the connection after the connection is established, and there is no disclosure regarding reception control of a connection establishment request. Further, even if the admission control of Patent Document 2 is applied to a connection establishment request, retransmission packets are treated uniformly regardless of the number of retransmissions, that is, the holding time. Even in Non-Patent Document 1, when congestion occurs, retransmission packets are uniformly discarded regardless of the number of retransmissions, that is, the hold time.

  In this way, in the above-described prior art, since each SYN packet is handled uniformly regardless of the length of the holding time on the packet receiving side, there is a request that can be received in a short time, but after a long holding time. However, there is a technical problem that a request that cannot be accepted occurs, and that the connection acceptance is unfair.

  An object of the present invention is to provide a connection establishment request accepting method, apparatus and program, and a connection establishment requesting apparatus capable of solving a number of connection establishment requests in a fair manner by solving the above-described problems of the prior art.

In order to achieve the above object, the present invention is characterized in that the following measures are taken.
(1) Establishment request detection means for detecting a connection establishment request, hold time determination means for determining the hold time of the detected establishment request, and accepting the detected establishment request preferentially as the hold time becomes longer And a reception selection means.
(2) The hold time determination means includes an identification means for identifying a connection establishment request, a hold time table for managing the hold time of each establishment request with the identification information, and the hold information based on the detected establishment request identification information. Means for searching a time table and determining a holding time.
(3) The hold time determining means extracts the hold time included in the detected establishment request.

According to the present invention, the following effects are achieved.
According to the above feature (1), since connection establishment requests having a longer holding time are accepted preferentially, the holding time of each connection establishment request can be made uniform.

  According to the above feature (2), since the hold time can be managed on the receiving side that receives the connection establishment request, the connection establishment request can be faired without adding a special function to the transmitting side that sends the connection establishment request. realizable.

  According to the above feature (3), since the holding time can be managed on the transmitting side that transmits the connection establishment request, the connection establishment request can be faired without increasing the load on the receiving side that receives a large number of connection establishment requests. realizable.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a network configuration of a communication / broadcast fusion system to which the present invention is applied, and transmits broadcast content in which television video content, data video content and data communication content are multiplexed. Broadcasting station 1, a viewer terminal 2 such as a television 2 a, a computer 2 b, and a portable terminal 2 c that receives broadcast waves transmitted from the broadcasting station 1 and reproduces broadcast content, and these viewer terminals 2 and the Internet The two-way response reception server 3 connected via the IP network 4 is a main configuration.

  The broadcast station 1 includes a broadcast server 1a that supplies broadcast content, and an OFDM transmitter 1b that digitally modulates and transmits the broadcast content. Each viewer terminal 2 uses, for example, a connection establishment function for establishing a connection with the response reception server 3 when an operation of transmitting an answer is performed by the viewer during viewing of the quiz program, and this connection is used. A response message transmission function for transmitting an answer (response message). The response message transmitted from each viewer terminal 2 is not limited to the answer to the quiz program or the questionnaire described above, but each viewer who is asked in the broadcast whether or not supplemental information is necessary regarding the broadcast content. A message to be sent in response to this is also included. When the viewer requests the supplement information by the response message, the requested supplement information is transmitted from the response reception server 3 to each viewer terminal 2 via the network 4.

  FIG. 2 is a block diagram showing a configuration of a main part of each viewer terminal 2, which receives and decodes broadcast waves to reproduce broadcast contents, and outputs TV video and data video from the speaker 26 and the display unit 25. A content reproduction unit 21 that performs the process, a destination address identification unit 22 that identifies the IP address of the response reception server 3 registered in the broadcast content, and an establishment request transmission unit 24 that establishes a connection by accessing the destination address. And a response message transmission unit 23 that transmits a response message using the connection.

  FIG. 3 is a functional block diagram showing the configuration of the main part of the response receiving server 3. Here, the configuration unnecessary for the description of the present invention is omitted.

  The establishment request detection unit 31 detects a connection establishment request transmitted from each viewer terminal 2. In this embodiment, a SYN packet with the SYN flag set is detected as a connection establishment request. The holding time determination unit 32 determines the holding time after the detected connection establishment request is first detected. The acceptance selection unit 33 selectively accepts or discards the detected connection establishment request based on the holding time, and returns a connection establishment response (SYN_Ack packet) to the accepted connection establishment request.

  FIG. 4 is a functional block diagram showing the configuration of the hold time determination unit 32 provided in the response reception server 3. The establishment request identification unit 321 transmits the SYN packet detected by the establishment request detection unit 31. It is uniquely identified based on the source IP address, destination IP address, sender TCP port number, and receiver TCP port number. The establishment request management unit 322 registers the reception time tr of the newly detected SYN packet in the hold time table 323 in association with the identification information. In the hold time table 323, the reception time tr of each connection establishment request is stored in association with the transmission source IP address, the destination IP address, the transmission side TCP port number, and the reception side TCP port number.

  The hold time determination unit 324 searches the hold time table 323 for the reception time tr of the SYN packet identified by the establishment request identification unit 321. Then, a holding time tw (= tc−tr) is calculated based on the reception time tr and the current time tc, and this is notified to the reception selection unit 33.

  FIG. 5 is a functional block diagram showing the configuration of the main part of the acceptance selection unit 33, which is detected by a plurality of queues 331 (331 a to 331 d) provided for each holding time tw and the establishment request detection unit 31. A weighted queuing unit 332 that links the SYN packet thus generated to each queue 331 based on the hold time tw notified from the hold time determination unit 32, and a SYN packet having a long hold time tw is preferentially received. A priority control unit 333 that selectively reads SYN packets from each queue 331 and a queue management unit 334 that manages SYN packets connected to each queue 331 are included.

  Next, the operation of the first embodiment of the present invention will be described with reference to the flowchart of FIG. FIG. 6 mainly shows the operation of the holding time determination unit 32 described with reference to FIG.

When a SYN packet is detected by the connection establishment request detection unit 31 in step S1, in step S2, the combination of the transmission source IP address, the destination IP address, the transmission side TCP port number, and the reception side TCP port number is It is extracted by the establishment request identifying unit 321 as identification information for uniquely identifying the SYN packet. In step S3, based on the extracted identification information, the hold time determination unit 324 determines whether or not the SYN packet entry has been registered in the hold time table 323. If it is not registered, the process proceeds to step S4, and the reception time tr of the detected SYN packet is set by the establishment request management unit 322 by its identification information (source IP address, destination IP address, transmission side TCP port number and reception). Side TCP port number) and newly registered in the hold time table 323.
On the other hand, if the detected SYN packet entry is already registered in the hold time table 323, in other words, if the detected SYN packet is a retransmitted packet, in step S5, the first reception time tr is held. The time determination unit 324 reads the hold time table 323.

  In the embodiment, a combination of the transmission source IP address, the destination IP address, the transmission side TCP port number, and the reception side TCP port number is used as identification information of each SYN packet. A hash value is calculated from these four pieces of information. The hash value may be used as identification information.

  In step S6, the elapsed time from the reception time tr to the current time tc is obtained as the hold time tw. In step S7, the hold time tw is notified to the acceptance selection unit 33 in association with the identification information of the SYN packet.

  Returning to FIG. 5, in the reception selection unit 33, each SYN packet is connected to one of the queues 331 based on the hold time tw notified from the hold time determination unit 32 in the weighting queuing unit 332. In this embodiment, threshold values (tw1, tw2, tw3) relating to the hold time tw are set for each queue. If 0 ≦ tw <tw1, the queue is connected to the queue 331d, and if tw1 ≦ tw <tw2, the queue 331c is connected. If tw2 ≦ tw <tw3, the queue is connected to the queue 331b. If tw3 ≦ tw, the queue is connected to the queue 331a.

  In the priority control unit 333, the SYN packet is read from each queue 331 at a frequency according to the weighting rule in the weighting queuing unit 332. In this embodiment, if SYN packets are connected to the queue 331a, all of them are read preferentially. If no SYN packet is connected to the queue 331a, all SYN packets connected to the queue 331b are preferentially read. If no SYN packet is connected to any of the queues 331a and 331b, all SYN packets connected to the queue 331c are read preferentially. If no SYN packet is connected to any of the queues 331a, 331b, and 331c, the SYN packet in the queue 331d is read.

  The queue management unit 334 measures the elapsed time from the time when each SYN packet is linked to each queue 331, discards the packet after a predetermined time, and responds to the normally read SYN packet (SYN_Ack). Packet) to the user terminal 2.

  In the embodiment described above, the priority is set based on the hold time tw, which is the difference between the reception time tr of the SYN packet and the current time tc, but based on the number of times the SYN packet is retransmitted. A priority may be set. In this case, if the system is such that the waiting time is a function of the number of retransmissions, such as TCP, the waiting time RTO (Retransmission Time Out) until retransmission is doubled for each retransmission, the number of retransmissions is set as a parameter. It is also possible to obtain the standby time by function calculation as follows, and to set the priority based on this standby time.

  Further, in this embodiment, a description has been given of an example of a complete priority scheduling method in which a packet is not read from a lower queue unless there is no packet in the higher priority queue, but the present invention is limited to this. Instead, a weighted priority scheduling method in which packets are repeatedly read from each queue at a rate corresponding to the priority may be employed.

  7 and 8 are block diagrams showing the configuration of the second embodiment of the present invention, and FIG. 7 is a functional block diagram showing the configuration of the establishment request transmission unit 24 provided in the viewer terminal 2. 8 is a functional block diagram showing a configuration of the response reception server 3 that receives a connection establishment request from the viewer terminal 2, and in each case, the same reference numerals represent the same or similar parts.

  In the viewer terminal 2 of FIG. 7, the establishment request generation unit 241 of the establishment request transmission unit 24 includes a transmission source IP address, a destination IP address, a transmission side TCP port number, and a reception side TCP port number, and a SYN flag is set. Generate a SYN packet. The establishment request unit 242 transmits the SYN packet to the response reception server 3 and registers the initial transmission time ts in the establishment request management table 245 together with the identification information of the SYN packet. The establishment request unit 242 further determines that the connection establishment has failed if the SYN_Ack packet cannot be received even after a predetermined RTO has elapsed after transmitting the SYN packet, causes the retransmission unit 243 to wait for the SYN packet, The entry of the SYN packet that has successfully established the connection is deleted from the establishment request management table 245.

  The hold time update unit 244 identifies the SYN packet waiting in the retransmission unit 243, reads the initial transmission time ts from the establishment request management table 245, and calculates the elapsed time from the transmission time ts to the retransmission timing. Update and register each SYN packet as the hold time tw. The retransmission unit 243 causes the establishment request unit 242 to retransmit the SYN packet with the hold time tw updated and registered at a predetermined retransmission timing.

  In the response reception server 3 of FIG. 8, the establishment request detection unit 31 detects a connection establishment request (SYN packet) transmitted from each viewer terminal 2. The holding time extraction unit 32 extracts the holding time tw registered in the detected connection establishment request. The acceptance selection unit 33 selectively accepts or discards the detected connection establishment request based on the holding time tw, and returns a connection establishment response (SYN_Ack packet) to the accepted connection establishment request.

  FIG. 9 is a flowchart showing the operation of the present embodiment. Here, the operation of the establishment request transmission unit 24 provided mainly in the viewer terminal 2 is shown.

  In step S21, when a connection establishment request is instructed by the application, in step S22, the SYN flag is set, and the transmission source IP address, the destination IP address, the transmission side TCP port number, and the reception side TCP port number are registered. A SYN packet is generated by the establishment request generator 241. In step S23, an initial value (3 seconds in this embodiment) of RTO (retransmission timeout value) is set in the retransmission timer, and in step S24, a SYN packet is transmitted from the establishment request unit 242 to the response reception server 3. In step S25, the retransmission timer is started, and in step S26, the transmission time ts of the SYN packet is registered in the establishment request management table 245 in association with the identification information of the SYN packet.

  If a connection establishment response (SYN_Ack packet) is detected in step S27, the process proceeds to step S31, the corresponding entry is deleted from the establishment request management table 245, and the process ends. On the other hand, if the retransmission timer times out in step S28 without detecting a connection establishment response, it is determined in step S29 whether the retransmittable period (connection timeout) has ended. If completed, the SYN packet is discarded in step S32, the corresponding entry is deleted from the establishment request management table 245, and the process ends.

  If the retransmittable period has not expired, the process proceeds to step S30 and the RTO is updated to twice the current value. In step S33, the hold time update unit 244 calculates the hold time tw based on the reception time tr of the SYN packet registered in the establishment request management table 245 and the current time tc. In step S34, the hold time tw is updated and registered in the corresponding SYN packet of the retransmission unit 23. In step S35, the SYN packet in which the hold time tw is updated and registered is retransmitted from the establishment request unit 242 by the retransmission unit 243. In step S36, a retransmission timer starts.

  Thereafter, the process returns to step S27, and the above-described retransmission process is repeated until a connection is established based on the retransmitted SYN packet or until it is determined in step S29 that retransmission is not possible.

  In the acceptance response server 3 of FIG. 8, when the SYN packet is detected by the establishment request detection unit 31, the hold time tw is extracted by the hold time extraction unit 34 and notified to the reception selection unit 33. In the reception selection unit 33, each SYN packet is selectively received or discarded based on the hold time tw, as in the first embodiment.

  FIG. 10 is a block diagram showing a hardware configuration of the response receiving server 3. The CPU 81 as a main control device, a main memory 82 in which a main program is mounted, and a ROM 83 in which programs and parameters are stored in a nonvolatile manner. The main configuration includes a RAM 84 that provides a work area to the CPU 81, a network controller 85, and an internal bus 86 that interconnects these units 81 to 85. The main program can be implemented by installing a program recorded in a magnetic storage medium, an optical storage medium, or a magnetic optical storage medium in the response reception server 3.

  The configuration of the establishment request detection unit 31, the hold time determination unit 32, the reception selection unit 33, and the hold time extraction unit 34 described with reference to FIG. 8 and the operation of the flowchart of FIG. Operates according to the program of the main memory 82, the program of the ROM 83, and parameters, and is realized by the processing performed in cooperation with the main memory 82, the RAM 84, the network controller 85, and the like.

  In the above-described embodiment, it has been described that the response reception server 3 is provided with a connection establishment request reception function. However, the present invention is not limited to this, and as shown in FIG. The accepting device 5 is arranged between the network 4 and the response accepting server 3, and the accepting device 5 is provided with the establishment request detecting unit 31, the hold time determining unit 32, and the accepting selecting unit 33 described with reference to FIG. Only the selected connection establishment request may be relayed to the response reception server 3 at the subsequent stage. If the accepting device 5 is provided with a connection establishment request accepting function, the accepting device 5 may also be provided with a function of relaying a connection establishment response (SYN_Ack packet) returned from the response accepting server 3 to the viewer terminal 2. desirable.

1 is a block diagram showing a configuration of a communication / broadcast fusion system to which the present invention is applied. It is the block diagram which showed the structure of the principal part of each viewer terminal. It is the functional block diagram which showed the structure of the principal part of a response reception server. It is a functional block diagram of the holding time determination part with which a response reception server is equipped. It is the functional block diagram which showed the structure of the reception selection part. It is the flowchart which showed the operation | movement of the holding time determination part. It is a functional block diagram of 2nd Embodiment of the establishment request | requirement transmission part with which a viewer terminal is equipped. It is a functional block diagram of 2nd Embodiment of a response reception server. It is the flowchart which showed operation | movement of the establishment request | requirement transmission part with which a viewer terminal is equipped. It is the block diagram which showed the hardware constitutions of the response reception server. It is the block diagram which showed the other structure of the communication broadcasting fusion system with which this invention is applied.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Broadcasting station, 2 ... Viewer terminal, 2a ... Television, 2b ... Computer, 2c ... Portable terminal, 3 ... Response reception server, 4 ... IP network

Claims (12)

An establishment request detection means for detecting a connection establishment request;
A hold time determination means for determining the hold time of the detected establishment request;
A connection establishment request accepting apparatus, comprising: an acceptance selection unit that preferentially accepts the detected establishment request as the holding time becomes longer. The holding time determination means includes
An identification means for identifying a connection establishment request;
A hold time table for managing the hold time of each establishment request with the identification information;
The apparatus for accepting a connection establishment request according to claim 1, further comprising means for searching the hold time table with identification information of the detected establishment request and determining the hold time.   2. The connection establishment request accepting apparatus according to claim 1, wherein the holding time determination unit extracts a holding time included in the detected establishment request.   The apparatus for accepting a connection establishment request according to claim 1, wherein the holding time determination means represents the holding time by the number of detected retransmissions of the establishment request.   5. The connection establishment request accepting apparatus according to claim 4, wherein the holding time determination unit obtains the holding time by a predetermined function calculation using the detected number of retransmissions of the establishment request as a parameter.   6. The connection establishment request accepting apparatus according to claim 1, wherein the connection is a TCP connection, and the connection establishment request is a SYN packet.   3. The connection establishment request accepting apparatus according to claim 2, wherein the identification information of the establishment request is a hash value of a plurality of pieces of information unique to the establishment request. A means for generating a connection establishment request;
Means for transmitting the generated establishment request;
Means for re-sending an unaccepted establishment request;
Means for updating and registering the hold time of the establishment request in the establishment request to be retransmitted. In the method of accepting a connection establishment request that accepts a connection establishment request and establishes a connection,
A procedure for detecting a connection establishment request;
A procedure for determining the hold time of the detected establishment request;
And a procedure for accepting the detected establishment request preferentially as the holding time becomes longer. The procedure for determining the holding time includes:
A procedure for identifying a connection establishment request;
A procedure for managing the hold time of each establishment request with the identification information;
The method for accepting a connection establishment request according to claim 9, further comprising: a procedure for determining a holding time based on identification information of the detected establishment request.   The method for accepting a connection establishment request according to claim 9, wherein the procedure for determining the suspension time extracts a suspension time included in the detected establishment request. In the connection establishment request acceptance program that accepts connection establishment requests and establishes connections,
To a server on the network
A procedure for detecting a connection establishment request;
A procedure for determining the hold time of the detected establishment request;
A program for receiving a connection establishment request, wherein the detected establishment request is preferentially executed as the holding time becomes longer.

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